Human Body Systems and Homeostasis

The primary function of the respiratory system is the exchange of gases within the body.
Gas exchange involves taking oxygen ( $O_2$ ) in and moving carbon dioxide ( $CO_2$ ) out of the body.
Lungs: The primary organs used for breathing and gas exchange.
Capillaries: Tiny blood vessels that facilitate the transfer of gases between the respiratory and circulatory systems.
Alveoli: These are the specific sites of gas exchange located within the lungs.

The purpose of this system is to get nutrients and gases transported or circulated throughout the entire body.
Heart: The muscular organ that pumps the blood to maintain circulation.
Arteries: Blood vessels that carry blood away from the heart to the rest of the body.
Veins: Blood vessels that carry blood toward the heart from the rest of the body.
Red Blood Cells: Specialized cells responsible for carrying $O_2$ . - Hemoglobin: The protein in red blood cells that allows them to bind to and carry oxygen. - Sickle Cell Anemia: A condition where red blood cells cannot carry enough $O_2$ because their abnormal shape hinders their functionality.

The respiratory system and circulatory system work in tandem to support cellular life.
The respiratory system brings in $O_2$ from the environment.
The circulatory system move this $O_2$ to all the cells in the body.
Cells utilize this oxygen to produce $ATP$ (Adenosine Triphosphate), which is the usable form of energy for the body.

Immunity: Defined as the body's ability to protect itself from disease.
Pathogen: Any external agent that causes disease, commonly referred to as germs (e.g., viruses).
White Blood Cells (WBC): The primary cells of the immune system responsible for defense. - WBCs produce antibodies to fight infections. - Antigens: Markers found on pathogens (like viruses) that identify them as foreign. - Antibodies: Proteins produced by WBCs that have a specific shape designed to match and lock onto a specific antigen. - Pathogen Destruction: WBCs engulf and destroy pathogens once they are identified. - Memory: The immune system remembers the antigens for future exposure so that the pathogen can be destroyed more quickly next time.

The main function is to break down food to extract essential nutrients.
These nutrients are subsequently turned into usable energy ( $ATP$ ).
This conversion process occurs through cellular respiration, which relies on the nutrients provided by digestion.

The system is responsible for releasing chemical messages known as hormones throughout the body.
Hormones are used to maintain homeostasis, ensuring the body stays in a stable internal state.
Pancreas: A key organ in the endocrine system that regulates blood sugar levels ( $BSL$ ) through the production of two primary hormones: - Insulin: A hormone produced to lower $BSL$ after an individual eats. - Glucagon: A hormone produced to raise $BSL$ if an individual has not eaten for a while.
Negative Feedback: The process of insulin and glucagon working to stabilize blood sugar is a primary example of a negative feedback loop, which acts to bring the body back to its stable state.

Positive feedback is a process that amplifies responses or stimuli in the body rather than reducing them. - It often occurs in the context of hormones and other biochemical processes. - A common example of positive feedback is during childbirth, where the release of the hormone oxytocin increases contractions, leading to more oxytocin being released until delivery occurs.